The formulation of lubricants typically includes an additive package incorporating a variety of chemicals to improve or protect lubricant properties in application specific situations, particularly internal combustion engine and machinery applications. The more commonly used additives include oxidation inhibitors, rust inhibitors, antiwear agents, pour point depressants, detergent-dispersants, viscosity index (VI) improvers, foam inhibitors and the like. This aspect of the lubricant arts is specifically described in Kirk-Othmer "Encyclopedia of Chemical Technology", 3rd edition, Vol. 14, pp477-526, incorporated herein by reference. The inclusion of additives in lubricants provides a continuing challenge to workers in the field to develop improved additives of increased compatibility with the lubricant and other additives or new additives containing a multifunctional capability that can reduce the number of additives required in the formulation.
Considering the diversity of chemical structures represented by the plethora of additives incorporated in a typical lubricant formulation, and the quantity in which they are added, the artisan in the lubricant formulation arts faces a substantial challenge to provide a homogeneous formulation which will remain stable or in solution during inventory and during use. Lubricants, particularly synthetic lubricants of the type of interest in the instant invention, are usually hydrogenated olefins containing, optionally, mineral oil, ester lubricants and the like. Due to their hydrocarbon structure they are largely incompatible with polar additives such as antioxidants, antirust and antiwear agents, etc. Accordingly, in order to render the lubricants compatible with the polar additives large amounts of expensive polar organic esters must be added to the formulation. Useful commercial formulations may contain 20 percent or more of such esters as bis-tridecanol adipate or pentaerythritol hexanoate for example, primarily to provide a fully homogeneous lubricant blend of lubricant and additive.
Modifying the solvent properties of lubricants with solubilizing agents such as organic esters, while solving the problem of how to prepare stable blends with lubricant additives, creates or accentuates other performance related problems beyond the added burden of cost on the product. Accordingly, workers in the field seek to incorporate the desirable properties of additives into lubricants, without incurring the usual physical and cost liabilities. One approach is to incorporate polar functional groups into the lubricant molecule to thereby include the additive property inherent in that functional group or render the lubricant more compatible with polar additives.
One class of lubricants of particular interest in the present invention is synthetic lubricants obtained by the oligomerization of olefins, particularly C.sub.3 -C.sub.20 alpha olefins. Catalytic oligomerization of olefins has been studied extensively. Known olefin oligomerization catalysts include the Ziegler-Natta type catalysts and promoted catalysts such as BF.sub.3 or AlCl.sub.3 catalysts. U.S. Pat. No. 4,613,712 for example, teaches the preparation of isotactic alpha-olefins in the presence of a Ziegler type catalyst. Other coordination catalysts, especially chromium on a silica support, are described in the art. Of notable importance is the inventions described in U.S. Pat. Nos. 4,827,064 and 4,827,073 to M. Wu, incorporated herein by reference, where superior hydrocarbon lubricants are prepared having low methyl to methylene branch ratio by oligomerization of alpha olefins using reduced valence state Group VIB metal oxide catalyst on porous support. Also, U.S. Pat. Nos. 4,520,221, 4,568,786 and 4,658,079 to C. S. H. Chen et al., incorporated herein by reference in their entirety, disclose further advances in zeolite catalyzed olefin oligomerization to produce lubricants. These patents disclose processes for the oligomerization of light, or lower, olefins using zeolite catalyst such as ZSM-5.
The foregoing synthetic lubricants contain olefinic unsaturation as prepared by oligomerization of C.sub.3 -C.sub.20 olefins. This unsaturation provides a convenient site for the functionalization of these lubricants to augment their lubricant properties or enhance their compatibility with additives. The olefin bond in these lubricants can participate in a wide range of typically olefin reactions, including olefin metathesis. Olefin metathesis is well known in the art and is described in Olefin Metathesis by K.J.Ivin, published by Academic Press, wherein Chapter 7, incorporated herein by reference, describes olefin metathesis with acyclic unsaturated compounds containing functional groups. As described therein, it is known that unsaturated esters as well as other olefinic compounds containing polar groups can participate in the olefin metathesis reaction to provide an equilibrium mixture of functionalized olefins.
It is an object of the present invention to provide a process for the functionalization of unsaturated synthetic lubricants by olefin metathesis with alkenes containing polar groups.
Another object of the present invention is to provide a process for the production of lubricants containing property enhancing polar groups.
Yet another object of the invention is to provide novel lubricant mixtures from conventional lubricants and additive quantities of synthetic lubricants functionalized by olefin metathesis.